In order to be sure of attaining all of the significant EKGs for abnormal beats of a patient's heart, it is often necessary to attain those that occur during many hours of normal activity. What is known as a Holter device is carried by the patient. It generally has two sets of electrodes that are respectively attached to different places on the patient's chest and an amplifying channel for each set. Two sets of electrodes are required for enhanced resistance to noise and sensitivity to the detection of certain events. An analyzer that classifies any beat occurring in the signals as normal, abnormal or artifact is connected to the channel having less noise. Beats that are found to be abnormal are recorded so that they can be reviewed by a physician at a later time. By connecting this analyzer to one channel or the other EKGs for abnormal beats that appear only on the other channel are missed.